if she took the rat pup she'll eat rats, if she took it frozen thawed even better... Don't change unless its a last resort.. ball python can go months without eating it isn't uncommon the most important thing is keep an eye on her weight and if it starts to go down you need to start worrying. That being said here are a couple of tricks to try and help her eat..
Scent the room, meaning leave the rat pup next to her cage for the time it is defrosting if your feeding live you can use like a tubbereware container or something to keep it in, i usually do this for about 30 mins to an hour and i do it for all my snakes i get a higher feeding response this way. I was also able to switch my live feeder to f/t by doing this
Another thing is always feed at night about 30mins to an hour after lights go out balls are nocturnal so they are looking for food at night and that is the best time to try and feed
also try place the food in the cage overnight I'll leave a f/t feeder in all night and leave a cover over the front of the cage so it's completely dark and that too can do the trick
finally go to your local pet store and ask for used gerbil bedding (if you tell them why they should have no problem and give it away for free) and rub the rat in the bedding to get the gerbil scent all over it and then feed it to the snake. gerbils are more closely related to there native food and the scent is more attractive to them. This worked on my sub adult female that went on a 2 month feeding strike.
Additionally make sure if you are feeding f/t that the food is nice and warm, balls have heat pits across there top lip and can tell when the food is the ideal temp.
you can try all of the above tricks at the same time and that too could trigger a feeding response also you may want to try mice if rats aren't working although when it becomes an adult you'll find you are feeding it 2 to 4 mice at a time
If feeding f/t don't go to live unless an absolute last resort, i mean the snake is losing weight an you have tried all other option. Also make sure to only offer feed once a week more than that can stress the animal. also you can try force feeding but this should only be done if you know what you are doing and as a last resort. I ahve had snakes go on 4 to 5 month feeding strikes and they always come around and eat again don't stress out just yet also search youtube and google thats where i found all this info and its a great help
I hope this helps and that you can get her to eat soon good luck